Advisor(s)

Charles A. DiMarzio

Contributor(s)

Carey M. Rappaport

Date of Award

2008

Date Accepted

7-2008

Degree Grantor

Northeastern University

Degree Level

M.S.

Degree Name

Master of Science

Department or Academic Unit

College of Engineering. Department of Electrical and Computer Engineering.

Keywords

Electrical and computer engineering, Photothermal spectroscopy, Confocal microscope

Subject Categories

Photothermal spectroscopy--Mathematical models

Disciplines

Engineering

Abstract

Photothermal spectroscopy is a powerful tool to investigate the optical absorption and thermal characteristics of a sample. The photo-thermal effect, that is the basis for photothermal spectroscopy, is the conversion of optical energy into heat. Photothermal spectroscopy is implemented in a variety of methods. Biomedical imaging applications commonly implement the Photo-Thermo-Acoustic (PTA) method, that is based on measuring the acoustic pressure wave that propagates due to the photothermal effect, caused by absorption of energy from a heating laser. This research demonstrates photothermal spectroscopy using a coherent confocal microscope. The high accuracy of the interferometer, that is the heart of the coherent confocal microscope, in detecting small changes in position makes it intrinsically adequate to measure the thermoelastic expansion of the sample that results from the photothermal process. In this research Polyvinyl-Chloride (PVC) samples, constructed with different absorption coefficients, were tested using different heating light fluences. The results are compared against an approximate theoretical model and are found to be in good agreement. The Opto-Photo-Thermo-Elastic (Optical detection of elastic displacement changes due to the phototheraml process) technique is demonstrated as a first step toward extending the capability of confocal microscopes to image deeper into tissues than is presently possible, and to detect new modes of contrast, such as the thermoelastic coefficient.

Document Type

Master's Thesis

Rights Holder

Igal Eliyahu


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